The invention relates generally to displays, and more particularly, to a display for indicating the position of a target.
In certain displays for indicating the deviation of a target from a reference line and a reference position, information relating to azimuth, elevation, and range of the target is presented to the user of the display. One well known technique for accomplishing the above is the peepsight which presents azimuth and elevation deviation of the target from the line of sight of the peepsight combined with a front reticle which is used for size estimation of the target to determine its range. The above describes a visual engagement system where the target must actually be seen by the user before accurate aiming can occur. The target and sights are viewed by the foveal vision of the user and comparisons are made between the line of sight of the sights and the target position. Typically, the device upon which the sights are mounted is moved until the target position in relation to the line of sight is within certain azimuth and elevation tolerances.
In conventional gunsights such as the type used in rifles, the eye of the user must not only form an image of the target but must simultaneously form an image of the fork and blade sights mounted at opposite ends of the barrel of the gun. The eye of the user cannot focus clearly on both the target which is usually at a substantial distance, and the elements of the gunsight which are relatively close to the eye of the user. Substantial skill is required for the effective use of this type of aiming device. Also, where cross hair aiming devices are used, they likewise are placed close to the eye of the user whereas the target is at a distance. Visual engagement sights such as those described above are less efficient and may be made unusable in darkness, smoke and fog.
Another well known system for sighting a target is a cathode ray tube ("CRT") display where an aiming symbol is displayed to indicate the position of a target relative to an aiming point or line of sight and to a reference position. The information displayed may be generated by a radar beam which contacts the target or other such means including light beams which are bounced off the target. If the user also desires to visually engage the target, he may have to switch between viewing the CRT display and viewing the target through sights such as those described above. This switching can be undesirable in the case of a high speed target where the target may make large position changes in a relatively short time period. However, visual engagement of the target is required in some cases. A sighting system capable of presenting both the means for visual engagement of a target and the means for the display of electronic tracking data of the same target to a user in a way that the user may receive both simultaneously, i.e., without refocussing his foveal vision, would be desirable.